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  • Category: Science

    Effect of solubility of water on heating and cooling

    Puzzled about the effect of solubility of water on heating as well as on cooling? Know the answer to this & related science-based queries through the useful answers provided at this Ask Expert page.

    We know that solubility of a liquid is increased on heating.

    My query is-
    Suppose we have some normal temperature water and we keep on mixing sugar in it until it is saturated i.e. no more sugar can be mixed in it. Now we heat it to increase it's solubility and then add more sugar to mix in it until the mixture once again becomes saturated. Now, what will happen when water is cooled down? Will the normal temperature water show signs of low solubility as it showed earlier? How can excess sugar that was dissolved in water because of increased temperature remain dissolved in the water when it is cooled down?
  • Answers

    6 Answers found.
  • Usually if the over-solved solution is allowed a gradual cooling, undisturbed, crystallisation can happen. We can get the solid solute and some solution.

  • This phenomena has to be understood in a different way since we know that solubility of a soluble substances increases with the rise of the temperature. Here we get two components volume of solvent and nature of solute. More is the volume of the solvent, more solute would be required to make the same saturated at a particular temp. However, the capacity of the solute to be dissolved will take place till its last boiling point when the maximum solute will get dissolved to make saturated. Saturation is a point where no more solute is dissolvable.
    Once that point is attained( saturation of solute at a particular temperature ), the solute gets precipitated with the fall of the temperature. There would be no more precipitation once it attains the room temperature.
    We may get crystal of the dissolved substances on its super cooling.

  • The solubility of many salts or compounds in water depends on temperature also. Generally with increasing temperature the solubility increases and stops when the solution is saturated.

    The science of this is very simple and as the temperature increases the knitic energy of the solvent molecules increases as well as the lattice vibration energy of the solute material also icreases and the net effect is increased solubility.

    Surprisingly, though rare, there are some solid solute materials which do not obey this rule.

    The gases show a reversed trend for solubility in water and it decreases with increase of temperature.

    When a solution is cooled down, many times the solute starts recrystallization and separates out from the solution. This property is often used for cleaning of some materials for the impurities as the impurities remain suspended in the solution and pure crystals of the solute is formed while bringing down the temperature of concentrated solution.

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  • For a solute to get dissolved in a solvent temperature, volume of the solvent and the amount of solute are three variable factors. The general features are
    1. Higher the temperature higher the weight of the solute that goes into the same volume of the solvent.
    2.Higher the volume of the solvent more solute can be dissolved
    3Higher the amount of solute more solvent is required.
    At a given temperature the maximum amount of solute tha can go into a fixed volume of solvent isknown as its solubility. It can be expressed in grams per litre.
    Once no more solute will go into a solvent at particular temperature, the solution resulted is known as saturated solution. Here one point you should remember is the maximum temperature you can heat the solution should be below the boiling point of the solvent. Otherwise the solvent will get evaporated slowly leaving the solute as well as the dissolved particles other than the solut.
    When you make a saturated solution at a particular temperature, if you go on increasing the temperature the solution will become unsaturated and you can dissolve more solute. Alternatively if the temperature is coming down the solute starts crystallising and it will happen till the solution get stabilised at a particular temperature and once it reaches saturation level at that temperature no more solute will get crystallised. This is one of the methods we use to change the crystal habit and morphology. In our high school we learned how to make a paper weight in which the same methodology is used.
    The solubility of any solvent at a given temperature is constant. It will not vary if you heat it up and then lower it also.

    always confident

  • If we have prepared a saturated solution of sugar in water and heat it we can add more sugar to it this solution is called supersaturated solution. If we cool down this solution and the excess amount of sugar will be deposited in the bottom of the glass and it will become saturated solution will be formed.
    A saturated solution is a solution in which the maximum amount of solute is dissolved in a solvent.

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  • If we go on adding sugar in the solution of sugar and water after the solution reaches the saturation point, the sugar will be deposited at the bottom of the solution. There is no doubt about it. However, if we increase the temperature of the solution, the additional sugar will be dissolved because an increase in temperature increases the saturation point of the solution.

    Now, what would happen if the heated solution is cooled (to room temperature)? The excess sugar which was added beyond the saturation point would again be formed and deposited at the bottom of the solution and the solution will remain at the saturation point.

    "If you are killed in action, you go to Heaven. If you win, you rule this Earth (as beautiful as Heaven). That is why, O son of Kunti, take a firm resolve and fight!"-- Shrimad Bhagwad Gita

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